Wheelchair lift device

ABSTRACT

A wheelchair lift device including a platform located in the stepwell of a motorcoach for raising and lowering a wheelchair between a first position wherein the platform is in horizontal alignment with an elevated floor formed with the motorcoach and a second position wherein the platform is at ground level. The device includes foldable hinged sections that are positioned through a linkage and a rotatable arm to form steps for use by able-bodied persons and are extendible laterally outwardly relative to the stepwell so as to align the hinged sections along a horizontal plane and thereby form the platform for supporting the wheelchair.

This invention concerns elevator devices in general and moreparticularly a wheelchair lift device that can be used with a motorvehicle.

Co-pending patent application Ser. No. 839,320 filed Oct. 4, 1977,entitled "Wheelchair Lift Device" in the names of Peter Dudynskyj,Daniel Kline and James Hogan and assigned to the assignee of thisinvention discloses a lift device for use in a motorcoach that employs aparallelogram type linkage actuated by an expendable hydraulic cylinderfor converting a foldable step assembly into a horizontal supportplatform for wheelchair use. Linkages connected to a carriage that ismovable through a chain drive to positions which selectively locate thedeployed platform at the floor level of the motorcoach and at groundlevel so that a handicapped person in a wheelchair can gain entry andexit from the motorcoach.

The present invention concerns an improved wheelchair lift device of thetype described above but differs therefrom in that the direct chaindrive for moving the carriage is replaced by a rotatable arm that servesto move the support platform in an arc between the floor and groundlevel positions. In one form, the wheelchair lift device according tothe invention includes a pair of substantially vertically oriented guidebars secured to the body of the vehicle on the opposite sides of thedoorway that opens into a stepwell leading into the interior of thevehicle. A carriage is mounted on each of the guide bars for movementtherealong to three positions. A parallelogram linkage including a pairof substantially vertically oriented links connects each of thecarriages with a platform assembly which includes a plurality of hingedsections. Two of the hinged sections normally form a stairway providinga thread and riser when the carriage is in one of the three positionswhile another two of the hinged sections form a horizontal platform whenthe carriage is located in the other two positions. The linkage iscombined with a power-operated rotatable arm one end of which ispivotally connected to the vehicle and the other end is pivotallyconnected to and supports the hinged sections. The arrangement of thecarriage, the links and the hinged sections is such that when thepower-operated arm is pivoted from a horizontal position to a raisedvertical position, the hinged sections move laterally outwardly relativeto the doorway under the control of the linkage and cause the platformassembly to be formed into a horizontal support in line with the vehiclefloor. After the platform assembly is deployed, the arm then ispivotally movable to a lowered position so as to place the wheelchairsupport platform at ground level.

In another form of the invention, the parallelogram linkage and thecarriage are replaced with a planetary gear system that is combined withthe arm which serves to move the hinged sections from the normal foldedposition to the raised vehicle floor level position and the loweredground level position.

The objects of the present invention are to provide a new and improvedwheelchair lift device for a motor vehicle having a movable carriagewhich through a rotatable support arm and a pair of generally verticallyoriented link members supports a plurality of hinged sections thatnormally form a series of steps and by raising the arm from a horizontalposition to a vertical position, the steps can be converted into ahorizontal platform for supporting a wheelchair under the control of thelink members, to provide a new and improved wheelchair elevator that canbe incorporated in the stepwell of a bus and that includes a pluralityof hinged angularly related members which normally form a series ofsteps and are movable by a rotatable arm laterally outwardly relative tothe stepwell under the control of a parallelogram linkage so as to causethe hinged members to be horizontally aligned and form a platform forsupporting a wheelchair; to provide a new and improved wheelchair liftdevice for the stepwell of a bus that has a plurality of link membersfor controlling movement of a plurality of hinged sections which throughthe rotation of a support arm connected to the hinged sections arealternately formed into stairs for able-bodied persons and into ahorizontal support platform for a physically handicapped person using awheelchair; to provide a new and improved wheelchair lift device thatcan be located in the stepwell opening of a bus and has foldable hingedsections that are positioned through a rotatable arm and a planetarygear system to form steps and are extendible laterally outwardlyrelative to the opening by the upward pivotal movement of the arm so asto align the hinged sections along a horizontal axis and thereby form asupport platform for a wheelchair.

Other objects and advantages of the invention will be more apparent fromthe following details description when taken with the drawings in which:

FIG. 1 is a side elevational view showing a wheelchair lift device madein accordance with the invention and located in the stepwell of amotorcoach in the normal folded position;

FIG. 2 is an elevational view showing the wheelchair lift device of FIG.1 with the platform thereof being deployed in a horizontal plane in linewith the floor of the motorcoach;

FIG. 3 is a view of the wheelchair lift device similar to that shown inFIG. 2 with the platform being positioned at ground level;

FIG. 4 is a plane view of the wheelchair lift device taken on line 4--4of FIG. 2;

FIG. 5 is an enlarged view taken on lines 5--5 of FIG. 4;

FIG. 6 is a side elevational view of a modified form of the wheelchairlift device; and

FIG. 7 is a perspective view of the wheelchair lift device of FIG. 6.

Referring to the drawing and more particularly FIGS. 1, 2 and 4 thereof,a wheelchair lift device 10 made in accordance with the invention isshown positioned within the stepwell 12 of a motor vehicle 14 such as acoach or bus of the type used in mass public transit having the usualfloor 16 which is at an elevation substantially above ground level. Aswill be more apparent as the description of the invention proceeds, thewheelchair lift device 10 provides the usual two steps in the stepwell12 of the vehicle permitting normal entry and exit for able-bodiedpassengers. In addition, and when it is desired, the steps of thewheelchair device 10 can be converted through a rotatable arm into ahorizontal support for a wheelchair that can be moved between an alignedposition with the vehicle floor 16 and a ground level position. In thismanner, a physically handicapped person confined to a wheelchair can beserved by the vehicle 14.

More specifically, the wheelchair lift device 10 comprises a pair ofidentical frame members 18 and 20 spaced along an axis parallel to thelongitudinal axis of the vehicle 14 and located in the stepwell 12 andon the opposite sides thereof. The frame members 18 and 20 are securedin substantially vertical positions to the associated frame structure ofthe vehicle 14 and respectively include identical guide bars 22 and 24each of which is secured at the upper and lower ends to "U" shapedbrackets 25 and 26. As seen in FIG. 4, each of the guide bars 22 and 24has parallel side walls along its full length when viewed in crosssection. The side walls of each guide bar provide a track for supportinga carriage 28 that is movable along the associated guide bar. In thisconnection, it will be noted that each carriage 28 includes a housingcomprising a support plate 29 rigidly formed with a pair of brackets 30and 31. An upper pair of rollers 32 and 33 and a lower pair of rollers34 and 35 are mounted on the brackets 30 and 31 of each carriage 28. Therollers engage the flat side walls of the associated guide bar and alloweach carriage to move freely upwardly and downwardly between thepositions shown in FIGS. 1, 2 and 3.

It will be noted that the aforementioned steps form a part of theplatform 38 which is located in the stepwell 12 and consists of aplurality of hinged sections that extend between the guide bars 22 and24 as seen in FIG. 4. As best seen in FIG. 1, the platform 38 includes apair of planar base sections 40 and 42 which are pivotallyinterconnected at their inner ends by a pivotal connection 44 formovement about a horizontal axis that is substantially parallel to thelongitudinal axis of the vehicle. As seen in FIG. 5, a torsion spring 45is wound about the pin which interconnects the base sections 40 and 42and constitutes the pivotal connection 44. One leg of the spring 45 isfixed with the base section 40 and the other leg is fixed with the basesection 42. The spring 45 continuously biases the base sections to thealigned position of FIGS. 2, 4 and 5, and stops members 46 and 47respectively fixed with the base sections 40 and 42, serve to assurethat the base sections stay in the aligned position.

The platform 38 is shown in the collapsed or folded position in FIG. 1wherein it is disposed adjacent to a vertical back wall 48 formedrigidly with the body of the vehicle 14. In the folded position, thebase section 40 is located in a vertical plane adjacent back wall 48while the base section 42 is located in a horizontal plane. The basesections 40 and 42 support a planar tread member 49 and a planar risermember 50 that constitute additional hinged sections of the platformextending between the guide bars 22 and 24. The riser member 50 has oneend connected by a pivotal connection 52 to the base section 42intermediate the ends thereof. The other end of the riser member 50 isconnected to one end of the tread member 49 by a piano hinge thatprovides a pivotal connection 54. The other end of the tread member 49is connected to the base section 40 by a pivotal connection 56 adjacentthe outer end of the base section 40. The base section 42, betweenpivotal connections 52 and 44, and the base section 40, between pivotalconnections 44 and 56, are respectively formed with wells 58 and 60having a depth, width and a longitudinal length that suitablyaccommodates the thickness, width and longitudinal length of theassociated tread and riser members 49 and 50 so as to allow storage ofthe latter when the platform 38 is deployed to the extended or unfoldedposition shown in FIGS. 2 and 4. In addition, base section 40 isprovided with a roller 61 which contacts the back wall 48 when theplatform 38 is in the position of FIG. 1.

The deployment of the platform 38 to the unfolded position of FIGS. 2and 4 is realized through the rotational movement of a support arm 62while under the control of a linkage incorporated with each of thecarriages 28. The linkage includes parallel support link members 64 and66. As seen in FIG. 1, the link members 64 and 66 are substantiallyvertically oriented, and are carried by the carriage 28. The link member64 has the upper portion thereof pivotally connected to the carriage 28by a pivotal connection 68 while the lower end is pivotally connected tothe inboard end of the base section 42 by the pivotal connection 44which also connects the base section 42 to the base section 40. The linkmember 66 has its upper end pivotally connected to the carriage 28 by apivotal connection 70. The lower end of the link member 66 is connectedto the base section 42 through a bracket 72 located intermediate theinboard and outboard ends of base section 42 and by a pivotal connection74.

A chain drive, which includes an endless chain 76 and a pair ofrotatable sprockets 78 and 80 carried by bracket 26, is incorporatedwith the lower end of each of the frame members 18 and 20 for moving thearm 62 from the horizontal position of FIG. 1 to the raised verticalposition of FIG. 2 and the lowered vertical position of FIG. 3. It willbe noted that the sprocket 80 of the frame members 18 and 20 aredrivingly interconnected by a common shaft 82 which extends between theframe members and is driven by a reversible hydraulic rotary motor 84.The sprocket 78 is rigidly connected with the arm 62 so upon rotationaldrive being directed to sprocket 78, the arms 62 associated with theframe members 18 and 20 are movable together from the normal position ofFIG. 1 to either the raised position of FIG. 2 and then to the loweredposition of FIG. 3. During such movement, the platform 38 under thecontrol of the linkage connected to the carriages 28 is moved as a unitbetween the latter mentioned positions.

From the above description, it should be apparent that when thewheelchair lift device 10 has the parts thereof located in the normalposition as seen in FIG. 1, the tread and riser members 49 and 50 aredisposed in substantially mutually perpendicular planes so as to formthe riser and tread portions of one step while the outboard end of thebase section 42 forms the tread portion of a second step. Thus, anable-bodied person can gain entrance into the vehicle 14 by firststepping on the outer end of the base section 42 and then on the treadmember 49 and finally on the floor 16 of the vehicle. If, however, aphysically handicapped person in a wheelchair should wish to enter thevehicle 14, the vehicle operator actuates a control valve of a suitablehydraulic control system (not shown) that directs pressurized fluid tothe hydraulic rotary motor 84. This causes the shaft 82 to drive thesprocket 80 of each of the frame members 18 and 20 in a counterclockwisedirection with similar driving rotation of the sprocket 78. This, inturn, results in counterclockwise rotation of the arm 62 from the FIG. 1position to the FIG. 2 position. Although not shown, suitable means canbe positioned on the vehicle body 14 that would be engaged by a portionof the arm 62 as it reaches the position of FIG. 2 to automaticallydiscontinue flow of pressurized fluid to the motor 84. As the arm 62rotates in this manner, it carries the base section 42 outwardlyrelative to the stepwell 12 under the control of the link members 64 and66 with the carriage 28 being moved upwardly along the associated guidebar. This movement of the arm 62 continues until the base sections 40and 42 are horizontally aligned as seen in FIG. 2. In this connection,as the arm 62 raises the base sections 40 and 42, the roller 61 movesalong the back wall 48 under the influence of the spring 45 and contactsthe lower inclined surface of a ramp member 86. As the arm 62 continuesits movement towards the FIG. 2 position, the clockwise rotation of thebase section 40 by the spring 45 causes the tread and riser members 49and 50 to move towards their stored positions in the wells 58 and 60.Also, during such time, the base section 42 is maintained in horizontalposition by the link members 64 and 66 as the carriage 28 is movedupwardly along the associated guide bar. When the arm 62 reaches theFIG. 2 position, the platform 38 is fully deployed to form a horizontalsupport surface for the wheelchair. It will be noted that although, notshown, suitable means can be provided on the vehicle body 14 that wouldbe engaged by a portion of the arm 62 when it reaches the position ofFIG. 2 so as to automatically discontinue flow of pressurized fluid tothe motor 84. On the other hand, the automatic stop of the motor 84 canbe overridden by the operator maintaining the control valve in an "on"position so as to cause the arm 62 to continue to rotate from the FIG. 2position to the FIG. 3 position. As the arm 62 moves between the lattermentioned positions, the carriages 28 move downwardly along theassociated guide bars and continue to maintain the platform 38 in ahorizontal attitude. Once the arm 62 reaches the position of FIG. 3, theplatform 38 is at ground level and the flow of pressurized fluid to themotor 84 can be automatically discontinued as described above. Thewheelchair can then be rolled onto the platform 38 and locked intoposition. The vehicle operator then reverses the procedure, causing thedrive sprockets 78 and 80 to be driven in a clockwise directionresulting in the arms 62 synchronously rotating in a clockwise directionto raise the carriages 28 and the platform 38 upwardly to the FIG. 2raised position wherein the platform 38 is horizontally aligned with thefloor 16. Again, the motor 84 can be either manually or automaticallystopped and the wheelchair then can be rolled onto the floor 16.Afterwards, the motor 84 can again be energized to return the arm 62 andplatform 38 to the folded position of FIG. 1. It will be noted that asthe platform moves from the FIG. 2 position to the FIG. 1 position, theroller 61 will contact the upper inclined surface on the range member 86to initiate the counterclockwise rotation of the base section 40 aboutpivotal connection 44 to return the various parts of the platform 38 tothe folded position of FIG. 1 wherein the steps are formed for normalusage of the vehicle entrance.

Although not shown, it will be understood that the outer end of the basesection 42 can be provided with a tapered ramp portion so as tofacilitate rolling of the wheelchair onto the platform 38 when thelatter is in the ground level position of FIG. 3. Also, in order toeliminate the possibility of an over-center action that could preventthe tread and rise members 49 and 50 from properly returning to the stepforming position of FIG. 1 after they are located in the alignedposition of FIG. 2, the tread and riser members 49 and 50 can be sizedso that the center of the piano hinge or pivotal connection 54 isslightly above a horizontal plane passing through the centers of pivotalconnections 52 and 56 when the platform 38 is in the FIG. 2 position.Another manner of accomplishing the same result would be to incorporatea spring at the pivotal connection 54 which would continuously bias thetread and riser members 49 and 50 towards the step forming position ofFIG. 1.

FIGS. 6 and 7 show another form of the invention disclosed in FIGS. 1-5,and it will be noted that parts of the FIGS. 6 and 7 constructioncorresponding to the parts in the above-described wheelchair lift device10 are identified by the same reference numberals but primed.

As seen in FIGS. 6 and 7, the wheelchair lift device is generallyindicated by the reference numeral 90 and, as in the case withwheelchair lift device 10, includes a pair of identical operatingmechanisms positioned on the opposite sides of a stepwell 12' thatprovides entrance to the interior of the motorcoach vehicle 14'. Also,each of the operating mechanisms comprises a support arm 62', theoutboard end of which is mounted to the body of the vehicle 14' forrotation about a horizontal axis extending longitudinally of thevehicle. The other end of the arm 62' is connected to the inboard end ofbase section 42' of the platform 38' by a pivotal connection 44' whichalso serves to pivotally interconnect the base section 42' to the basesection 40'. In addition, a sprocket wheel 92 is nonrotatably fixed tothe base section 42' with its center located at the center of thepivotal connection 44'.

The platform 38' also includes a tread member 49', one end of which isconnected to the base section 40' by a pivotal connection 56' while theother end is connected to a riser member 50' by a pivotal connection54'. It will be noted that as seen in FIG. 6, the lower end of the risermember 50' is spaced from and not connected to the base section 42'.Instead, a link 94 is provided which has one end pivotally connected tothe base section 42' by a pivotal connection 96 while the other end ispivotally connected to the tread and riser members by the pivotalconnection 54'. Both base sections 40' and 42' have wells 58' and 60'located in the upper surfaces there of for accomodating the tread andriser members 49' and 50' in a manner as explained with respect to thecorresponding parts in the wheelchair lift device 10. Also, although notshown, a torsion spring is provided at the pivotal connection 44' forcontinuously providing a clockwise bias to the base section 40' aboutthe pivotal connection 44' in the manner explained with respect towheelchair left devoce 10.

The drive system for the wheelchair lift device 90 includes a reversiblerotary hydraulic motor 84' carried by the vehicle body and having theoutput shaft thereof formed with a worm 98. The worm meshes with a wormgear 100 which is rigidly fixed with a sprocket wheel 102 mounted on ashaft 104 that is carried by the vehicle and extends from one side ofthe stepwell 12 to the other for rigid connection with an identicalsprocket wheel 102. As endless chain 106 connects the sprocket wheel 102with a sprocket wheel 108 fixed with a stub shaft 110 which is rotatablycarried by the body of the vehicle 14. It will be noted that the shaft110 extends through a sprocket wheel 112 which is fixed with the body ofthe vehicle and is connected to the sprocket wheel 92 by an endlesschain 114. The sprocket wheels 92 and 112 are identical in size andserve to provide a planetary gear system for the wheelchair lift device90 as will be explained hereinafter. One further difference in thewheelchair lift device 90 over the wheelchair lift device 10 is that thebase section 40' is provided with an extension member 116 which ispivotally connected to the end of the base section 40' by a pivotalconnection 118. Although not shown, a torsion spring is provided at thepivotal connection 118 for continuously urging the extension member 116into alignment with the base section 40'. A pair of stop members 120 and122 serve to maintain the extension member 116 in alignment with thebase section 40'.

As seen in full lines in FIGS. 6 and 7, the wheelchair lift device 90 isin the collapsed or folded position. When it is desired to deploy theplatform 38', the vehicle operator actuates a control valve of asuitable hydraulic control system (not shown) that directs pressurizedhydraulic fluid to the hydraulic rotary motor 84'. The worm 98 thendrives the sprocket wheels 102 in a counterclockwise direction throughthe worm gear 100. Similar rotation is directed to the sprocket wheels108 which through the stub shafts 110 cause the arms 62' tosynchronously rotate counterclockwise towards the raised positionindicated by Roman numeral I. As the arms 62' move towards the raisedposition, the extension member 116 is initially cammed counterclockwiseabout the pivotal connection 118 by the camming surface 124 attached tothe floor 16'. As the platform 38' continues its upward movement, thetorsion spring at the pivotal connection 44' causes the base section 40'to rotate in a clockwise direction about pivotal connection 44' therebycausing the tread member 49' and the riser member 50' to move towardsand into the wells 58' and 60' under control of the links 94 when thearms 62' reach the fully raised position indicated by the Roman numeralI. During such movement, the base section 42' maintains a horizontalattitude at all times. This is so because sprocket wheel 112 is fixedwith the body of the wheel and therefore does not rotate. Similarly,sprocket wheel 92 is fixed to the inboard end of the base section 42'and does not rotate relative thereto. Accordingly, when the arm 62'rotates about its support, the chain 114 causes a planetary action whichresults in the base section 42' maintaining the horizontal position asit moves upwardly to the raised floor level position. A similar actionoccurs when the arms 62' are rotated counterclockwise from the raisedposition to the lowered ground level position indicated by the Romannumeral II. Once the platform 38 is at the ground level position, awheelchair can be rolled onto the aligned base section 40' and 42' andthe vehicle then reverses the procedure causing the drive sprocket wheel102 to be driven in a clockwise direction thereby raising the arms 62'and the platform 38 in an arc to the raised floor level position so thewheelchair can be rolled onto the vehicle floor 16'. Afterwards, thearms 62' are returned to the full line position so the platform 38' canonce again be used for normal stairway entry to the motorcoach.

As in the case with the wheelchair lift device 10, the control systemfor operating the hydraulic motor 84' can include automatic stop meansfor locating the arms 62' in the raised floor level position and thelowered ground level position.

Various changes and modifications can be made to this constructionwithout departing from the spirit of the invention. Such changes andmodifications are contemplated by the inventor and he does not wish tobe limited except by the scope of the appended claims.

What is claimed is:
 1. A lift device having a foldable platform locatedin the doorway of a motor vehicle for raising and lowering a loadbetween a first position wherein the platform is in horizontal alignmentwith a floor formed with the motor vehicle and a second position whereinthe platform is at ground level, said device comprising a pair ofsubstantially vertically oriented guide bars secured to said vehicle atthe opposite sides of said doorway, a carriage mounted on each of saidguide bars for controlling movement of said platform between said firstand second positions, said platform comprising a pair of base sectionsand a tread section and a riser section adapted to be moved from a stepforming position wherein adjacent sections are angularly disposedrelative to each other to a load support position wherein said adjacentsections are located in a horizontal plane, a first pivot connectionjoining said pair of base sections for pivotal movement about ahorizontal axis, a second pivot connection joining said tread sectionand said riser section for pivotal movement about an axis parallel tosaid horizontal axis, third and fourth pivot connections joining saidriser section and said tread sections to said base sections whereby saidriser and tread sections are movable by said base sections between saidstep forming position and said load support position, a spring locatedat said first pivot connection for normally urging said base sectionstowards the load support position, a linkage connecting the carriagewith said base sections for supporting the platform, an arm having oneend rotatably mounted to said vehicle and the other end pivotallyconnected to one of said base sections for moving said platform in anarc between said first and second positions and said step formingposition, and means operatively connected to said arm for rotating saidarm and thereby moving the platform between said first and secondpositions when the base sections are in said load support position andinto said step forming position.
 2. A lift device having a foldableplatform located in the doorway of a motor vehicle for raising andlowering a load between a first position wherein the platform is inhorizontal alignment with a floor formed with the motor vehicle and asecond position wherein the platform is at ground level, said devicecomprising a pair of substantially vertically oriented guide barssecured to said vehicle at the opposite sides of said doorway, acarriage mounted on each of said guide bars for controlling movement ofsaid platform between said first and second positions, said platformcomprising a pair of planar base sections, a tread section and a risersection adapted to be moved from a step forming position whereinadjacent sections are angularly disposed relative to each other to aload support position wherein said adjacent section are located in ahorizontal plane, a first pivot connection joining said pair of basesections for pivotal movement about a horizontal axis, a second pivotconnection joining said tread section and said riser section for pivotalmovement about an axis parallel to said horizontal axis, third andfourth pivot connections joining said riser section and said treadsections are movable by said base sections between said step formingposition and said load support position, a spring located at said firstpivot connection for normally urging said base sections towards the loadsupport position, a linkage including a pair of link members connectingthe carriage with said base sections for supporting the platform, an armhaving one end rotatably mounted to said vehicle and the other endpivotally connected to one of said base sections for moving saidplatform in an arc between said first and second positions and said stepforming position, and means operatively connected to said arm forrotating said arm and thereby moving the platform between said first andsecond positions when the base sections are in said load supportposition and into said step forming position.
 3. A lift device having afoldable platform located in the doorway of a motor vehicle for raisingand lowering a load between a first position wherein the platform is inhorizontal alignment with an elevated floor formed with the motorvehicle and a second position wherein the platform is at ground level,said device comprising a pair of substantially vertically oriented guidebars secured to said vehicle at the opposite sides of said doorway, acarriage mounted on each of said guide bars for controlling movement ofsaid platform between said first and second positions, said platformcomprising a pair of planar base sections, a tread section and a risersection adapted to be moved from a step forming position whereinadjacent sections are angularly disposed relative to each other to aload support position wherein said adjacent sections are located in ahorizontal plane, a first pivot connection joining said pair of basesections for pivotal movement about a horizontal axis, spring meansconnected to said base sections and biasing said base sections into saidload support position, a second pivot connection joining said treadsection and said riser section for pivotal movement about an axisparallel to said horizontal axis, third and fourth pivot connectionsjoining said riser section and said tread sections to said base sectionswhereby said riser and tread sections are movable by movement of one ofsaid base sections between said step forming position and said loadsupport position, a linkage including a pair of parallel link memberspivotally connecting the carriage with one of said base sections forsupporting the platform, an arm having one end rotatably mounted to saidvehicle and the other end pivotally connected to one of said basesections for moving said platform in an arc between said first andsecond positions and said step forming position, a roller mounted on theother of said base sections and engageable with a cam connected to saidfloor for causing said other of said base sections to pivot about saidfirst pivotal connection against the bias of said spring as saidplatform is moved from said first position to said step formingposition, and hydraulic rotary motor means operatively connected to thearm for rotating said arm and thereby moving the platform between saidfirst and second positions when the base sections are in said loadsupport position and into said step forming position.